[llvm] [VPlan] Use VPInstruction for VPScalarPHIRecipe. (NFCI) (PR #129767)

[via llvm-commits]

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@@ -458,6 +464,13 @@ Value *VPInstruction::generate(VPTransformState &State) {
   }
 
   switch (getOpcode()) {
+  case Instruction::PHI: {
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ayalz wrote:

Somewhere it should be documented that VPInstructions of PHI opcode are used to model header phi's only.

https://github.com/llvm/llvm-project/pull/129767